1. Field of the Invention
The present invention relates to the field of electro-optical packaging. Specifically, an embodiment of the invention is directed to an apparatus and method for integrating an optical transceiver with a surface mount package.
2. Related Art
As system operating speeds rise, high speed data transmission becomes an important aspect of full system performance. Optical data transmission media are advantageous. Optical transceivers facilitate high speed transmission of data over optical fiber media. Electrical design facilitating high performance at high frequencies are crucial.
Optical transceivers incorporate a light source, often a laser diode (LD) for data transmission, its driver, a photodetector, its amplifier, electrical connections, and an optical system coupling the laser and photodetector to the transmission medium, all integrated in a single package. Optical transceivers with lasers differing in output wavelength, mode, and power may be selected according to a variety of applications. Optical transceivers are integral parts of many electronic data systems, where they receive control and data for transmission from and send feedback and data received to logic devices such as a serializer/deserializer (SERDES). Optical transceivers, typically with relatively few connecting pins, are either mounted directly upon a printed circuit board (PCB), or connected via a socket, which is itself mounted directly upon the PCB.
Optical transceivers, due to the short service lives of their lasers relative to other system components or due to a change in application, such as from short to long haul transmission, may require replacement before other system components. This is potentially wasteful and costly. The socket connection option is a conventional way to address this problem.
In the conventional arrangement, pins of the optical transceiver are connected, individually, to a SERDES device or another logic chip, typically with a larger number of connections than the optical transceiver. This scheme is problematic because the optical transceiver produces a large footprint upon the PCB mounting it. Physically, the optical transceiver requires an inordinate portion of the limited space available on the PCB, reducing the functionality of the PCB by displacing other functional components, and complicating required routing interconnections between functional components.
Further, both the conventional arrangement scheme and socket connection scheme have detracting electrical characteristics, such as high impedance and other poor performance characteristics at high frequencies, tending to limit data transfer speeds. It is also difficult in these schemes, due to the relative paucity of connection pins on the optical transceivers, to integrate the full functionality of the SERDES. Further, the conventional scheme is fraught with a number of fabrication related difficulties.
The first difficulty is that optical transceivers present a relatively large PCB footprint. Thus, their consumption of available PCB space complicates connection layout and reduces PCB space and connectivity available for mounting and connecting other components. Further, their high relative density and corresponding X-ray opacity, coupled with the large footprint prevents application of a non-destructive testing (NDT) modality common in PCB fabrication engineering, quality control, and failure analysis. Second, increases in functionality increase this footprint, correspondingly exacerbating the first difficulty. A third difficulty in mounting and connecting optical transceivers directly to PCBs is the requirement of special manufacturing and inspection techniques.
One such manufacturing technique is to avoid solder reflow. Conventionally, this is accomplished in one way by soldering a special socket for the optical transceivers to the PCB and connecting the optical transceiver thereon. However, this requires additional steps, handling, and components. It also correspondingly increases fabrication and unit costs. Further, sockets complicate and degrade the electrical connectivity between the optical transceivers and the SERDES and other components, with corresponding reduction in data transfer speeds.
Another special fabrication technique of the conventional art is to employ solder reflow, and simply withstanding the correspond high temperatures. However, the internal constitution of optical transceivers incorporates microminiature optics with critical alignments. These are delicate and correspondingly very temperature sensitive. Laser diodes within the optical transceivers are also temperature sensitive. Common optical transceivers may thus be rendered inoperable by exposure in conventional fabrication to the high temperatures associated with reflow. Especially robust optical transceiver packages, made to withstand high reflow temperatures, would be more expensive, thus increasing unit costs.
For inspection, either non-X-ray NDT techniques are required, in the conventional art, or disassembly and/or destructive testing must be used. Non-X-ray NDT may be considerably more expensive than X-ray NDT, given the common application of X-ray NDT in PCB fabrication. The alternatives, disassembly or destructive testing obviate the inherent advantages of NDT, and are also correspondingly expensive and wasteful.
What is needed is a method and/or apparatus that effectively integrates optical transceivers with PCBs and/or other electronic platforms, removably and without a large PCB footprint. What is also needed is a method and/or apparatus that integrates optical transceivers with PCBs and/or other electronic platforms, which has good electrical connectivity attributes and enables full functionality of connected logic and facilitates data transfer speeds at high frequencies. What is further needed is a method and/or apparatus that integrates optical transceivers with PCBs and/or other electronic platforms, which has good thermal and other mechanical characteristics, facilitating effective dissipation of heat accompanying high frequency circuit operation and laser operation, and withstands stresses and strain associated with inserting, changing, and removal of fiber optic connections thereto. What is needed further still is a method and/or apparatus that effectively integrates optical transceivers with PCBs and/or other electronic platforms, which achieves the foregoing advantages while facilitating employment of fabrication and inspection techniques which do not require increased complexity of handling, robustness of components, or cost.
Embodiments of the present invention provide an apparatus and method that effectively integrates optical transceivers with PCBs and other electronic platforms, removably and with a relatively small PCB footprint. Embodiments of the present invention also provide an apparatus and method that integrates optical transceivers with PCBs and other electronic platforms, which has good electrical connectivity attributes, facilitating data transfer speeds at high frequencies and enabling full interfunctionality with connected logic. Further, embodiments provide an apparatus and method that integrates optical transceivers with PCBs and/or other electronic platforms, which has good thermal and other mechanical characteristics, facilitating effective dissipation of heat accompanying high frequency circuit operation and laser operation, and withstands stresses and strain associated with inserting, changing, and removal of fiber optic connections thereto. Further still, embodiments provide an apparatus and method that effectively integrates optical transceivers with PCBs and other electronic platforms, which achieves the foregoing advantages while facilitating employment of fabrication and inspection techniques which do not require increased complexity of handling, robustness of components, or cost.
The present invention provides an apparatus and method that effectively integrates optical transceivers with PCBs and other electronic platforms, removably and with a relatively small PCB footprint. In one embodiment, a physical arrangement that integrates an optical transceiver with a PCB uses a relatively small portion of the space on the PCB (e.g., in comparison with the conventional art). Advantageously, this increases the functionality of the PCB circuit, by making ample room for mounting other functional components, and simplifying the routing of interconnections between functional components. Further, it facilitates X-ray NDT inspection of the PCBs.
The present invention provides, in one embodiment, an apparatus and method that effectively integrates optical transceivers with PCBs and other electronic platforms, which has good electrical connectivity attributes and enables full functionality of connected logic. Importantly, one feature of the present embodiment is that connectivity between the optical transceiver and the PCB is affected using relatively low impedance connectors that have corresponding characteristically high performance with high frequency electrical signals. Advantageously, this facilitates data transfer at high frequencies. A further advantage of this embodiment is that the connections enable efficient electrical interconnection and interfunctionality between the optical transceiver and logic components crucial to effective data transfer, such as SERDES devices.
The present invention further provides an apparatus and method that integrate optical transceivers with PCBs and/or other electronic platforms, which has good thermal and other mechanical characteristics. In one embodiment, the heat accompanying both high frequency circuit operation and laser operation is effectively dissipated. In one embodiment, the physical mounting of the optical transceiver to the PCB is buttressed by its own construction to effectively withstand the mechanical stresses and strains associated with inserting, changing, and removal of fiber optic connections to the optical transceiver required for optically coupling the laser and photodetector components of the transceiver to the optical fiber data transfer channel, and other mechanical forces.
In one embodiment, the present invention provides an apparatus and method that effectively integrate optical transceivers with PCBs and other electronic platforms, which achieves the foregoing advantages while facilitating employment of fabrication techniques which do not require increased complexity of handling, robustness of components, or cost. The present embodiment obviates sockets, a conventionally required component. Advantageously, dispensing with this heretofore required component further improves electrical performance. Also, the present embodiment is free of the constraints of fabrication related difficulties of the conventional art. Advantageously, this promotes efficiency and correspondingly reduces fabrication costs.